72004: LiveSync connector could not identify target channel

A LiveSync database connector read a change but could not determine which channel to publish it to, because the change had no _ablyChannel field. Only changes that specify a channel can be published.

What you should do

Make sure each change carries an _ablyChannel field naming the channel to publish to, at the top level of the change event rather than nested inside the document. This is normally set by the connector's aggregation pipeline.

Why it happens

The connector read a change that had no _ablyChannel field, so it could not tell which channel to publish it to. Only changes that carry a channel name in _ablyChannel can be published, and the field has to be at the root of the change event, not under a nested document.

What you'll see

The error is reported with code 72004 and HTTP status 400. The message is of the form no channel key in message <id>.